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OS 91 Surpass (silver top) - starts but then dies

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OS 91 Surpass (silver top) - starts but then dies

Old 11-18-2014, 04:55 AM
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Default OS 91 Surpass (silver top) - starts but then dies

My old (bought used) OS 91 Surpass (4s, silver top) keeps dying right after I start it. Recently it backfired when I leaned too much (ripped the engine box off the plane!) - after removing and starting the engine it ran fine, but the next time would not start. I found one of the two lifter springs was broken. I just happened to have a different wrecked OS 91 Surpass II, so I moved the springs over from that engine's head (NOT easy getting those spring keeper stays in place...).

Now the engine starts, but dies almost right away. I re-gapped the lifter gaps - between .04 and .1mm (though one side may be a bit tight), checked the carb needle setting (2nd ridge is tangential to the carb throat edge), checked the fuel tubing and tank (all good). The prop is a Xoar 14x8. The HS needle is now set to 2 full turns (per the manual) - though I think it was set at about 1 1/8 before (not sure about this). Even if 2 is too rich, I don't think it should kill the engine right after starting, right? I'd think the HS would only come into play around mid-throttle. Also the cylinder and bearings are in good shape.

Could the lifter springs that I used from my OS 91 Surpass II have a different tension than the old springs? They looked exactly the same. What am I missing here? My next step (tonight) will be to open the lifter gaps just a bit. And also might open the LS needle setting a touch.

Any suggestions would be appreciated!

Mike D

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